The invention relates to an improved container structure having good moisture and barrier properties and superior structural integrity. In addition, the unique barrier laminate structure does not require a tie layer to bond or adhere the barrier and stiffness layer. Additionally, the invention addresses an unique blend of a barrier and stiffness material in one layer to provide an excellent barrier structure. The unique structures can take the form of a paperboard based container as well as a blow molded bottle structure, both being recyclable due to the exclusion of a polyolefin-based tie layers. The structure relies on polyethylene terephthalate for structural integrity in combination with an amount of ethylene vinyl alcohol copolymer for its oxygen and moisture barrier properties. Further, in the paperboard based structure, the use of polyethylene terephthalate enhances structural integrity and prevents unwanted carton bulge.
The PET/EVOH based structures have many valuable benefits, they are recyclable, they have dimensional stability (bulge resistance), they provide flavor scalping resistance, they contain oxygen barrier properties, they have score crack resistance, they exhibit reduced contaminant migration, they have improved abuse resistance, they have improved printability and do not require tie layers.
Prior structures using various barrier materials have always used polyolefin materials or polyolefin based materials as tie layers or as product contact layers (matte) for heat sealability purposes. Use of these materials has made it extremely difficult to recycle the structures.
Structures and laminates as depicted in U.S. Pat. Nos. 4,284,671; 4,774,114; 4,929,482; 4,977,004; 4,528,219; 4,990,382; 4,883,696; 5,506,014; 5,320,889; 5,232,754; 4,675,219; and 4,564,541 all require the use of polyolefins or polyolefin based materials for producing the laminates or bottle structures disclosed therein. They all fall short of the novel recyclable polyolefin-free structure of the invention.
It is an objective of the present invention to provide an improved laminate container structure or blow molded bottle having good moisture and barrier properties and having superior structural integrity.
A further object of the invention is to provide a structure or bottle that does not require a tie layer to bend or adhere the barrier and stiffness layer.
It is a further objective of the present invention to provide a structure or bottle that is recyclable.
Paperboard-based laminate structures which accomplish the above-identified desired benefits and have the required properties include, but not limited to the following:
Heat sealable polyethylene terephthalate currently include an acid modified polyethylene terephthalate, such as CRYSTAR(copyright) 4486 sold by DUPONT, glycol-modified polyethylene terephthalate, such as KODABOND(copyright) PETG sold by Eastman Chemical.
The bracketing of the above-structures indicate that during formation, these materials are coextruded together.
Trials were run confirming that polyethylene terephthalate adhered directly to ethylene vinyl alcohol copolymer without the necessity of using tie layers. This is significant in that polyethylene terephthalate is recyclable and tie layers are not recyclable or degradable. Where high barrier ethylene vinyl alcohol copolymer was utilized (29% ethylene content), only a small amount was required to provide desired barrier properties (moisture and oxygen) and still have the structure recyclable.
In addition, the use of polyethylene terephthalate in combination with ethylene vinyl alcohol copolymer without the use of a tie layer produces a superior blow molded bottle. 
A thin layer of high barrier ethylene vinyl alcohol copolymer (29% ethylene content) is used between two layers of polyethylene terephthalate thereby producing a superior bottle structure for carbonated or non-carbonated beverages. A second blow molded bottle structure with polyethylene terephthalate as the outer layer and ethylene vinyl alcohol copolymer as the product contact layer would produce an excellent bottle for carbonated and non-carbonated beverages. A third structure is also contemplated wherein polyethylene terephthalate is the inside product contact layer and ethylene vinyl alcohol copolymer is the gloss layer.
A preferred polyethylene terephthalate for both paperboard and bottle structures is sold by Eastman Chemical under the name EASTACOAT(copyright) PET19860 polyethylene.
The bottle application is unique in that the polyethylene terephthalate bonds directly to the ethylene vinyl alcohol copolymer without non-recyclable environmentally unfriendly tie layers.
The above and other objects, features, and advantages of the present invention will become clear from the following description of the preferred embodiments thereof, taken in connection with the accompanying drawings.